爬虫一 发请求&定制请求&异常处理&配置代理

一、urllib库request

import urllib.request

url1 = "http://www.baidu.com"
image_url = 'https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality' 
            '=100&size=b4000_4000&sec=1561451694&di=4123b89e27e7f8d6091dfedc3e222d5a&src' 
            '=http://b-ssl.duitang.com/uploads/item/201711/01/20171101201000_UBjmK.jpeg'

'''方法一：urlopen'''
rep = urllib.request.urlopen(url=url1)     #发送请求并接收响应
#print(rep)
#print(rep.read().decode())   #读取内容，并将字节类型解码为字符串类型
# print(rep.geturl())       #获取url
# print(rep.getheaders())   #获取头信息
# print(rep.getcode())      #获取状态码
# print(rep.readlines())    #按行读取

rep2 = urllib.request.urlopen(url=image_url)
# with open('gaolu.jpeg','wb') as fp:       #保存读取的内容到文件
#     fp.write(rep2.read())

'''方法二：urlretrieve'''
rep3 = urllib.request.urlretrieve(image_url,'gl.jpeg')

二、urllib库parse

import urllib.parse

'''方法一：quote和unquote'''
url = 'http://www.baidu.com/index.html?name=狗蛋&pwd=123456'
ret = urllib.parse.quote(url)       #url编码,转换为url规定字符
print(ret)
ret2 = urllib.parse.unquote(ret)    #url解码
print(ret2)

'''方法二：urlencode'''
url2 = 'http://www.baidu.com/index.html'
data = {'name':'狗蛋',
        'age':15}

'''手动拼接url'''
lt = []
for k,v in data.items():
    lt.append(k + '=' + str(v))
query_string = '&'.join(lt)
print(query_string)
url3 = url2 + '?' + query_string
print(url)

'''urlencode拼接url'''
query_string2 = urllib.parse.urlencode(data)   #将字典格式的数据转为url格式
print(query_string2)

三、request.Rquest创建请求对象

import urllib.request
import urllib.parse

url1 = 'http://www.baidu.com/'

'''定制请求头，伪装自己——反'反爬'第一步'''
headers1 = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                         'AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'}

req = urllib.request.Request(url=url1,headers=headers1)       #构建请求对象
rep = urllib.request.urlopen(req)
#print(rep.read().decode())
print(rep.getheaders())

四、post请求

import urllib.request
import urllib.parse

post_url = 'https://fanyi.baidu.com/sug'

word = input('>>>:')
''' 构建post表单数据'''
data = {'kw':word,}
form_data = urllib.parse.urlencode(data).encode()    #将字典格式的数据转为url格式

headers1 = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                         'AppleWebKit/537.36 (KHTML, like Gecko) '
                          'Chrome/73.0.3683.86 Safari/537.36'}

req = urllib.request.Request(url=post_url,headers=headers1)

rep = urllib.request.urlopen(req,data = form_data)        #发送post请求

ret = rep.read().decode()

print(ret)

五、Ajax-get请求

import urllib.request
import urllib.parse

'''豆瓣排行榜接口：https://movie.douban.com/j/chart/top_list?type' 
      '=24&interval_id=100%3A90&action=&start=120&limit=20'''

url = 'https://movie.douban.com/j/chart/top_list?type' 
      '=24&interval_id=100%3A90&action=&'

dic_data = {'start':4,
            'limit':5}     #定制参数
data = urllib.parse.urlencode(dic_data)
url += data

headers1 = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                         'AppleWebKit/537.36 (KHTML, like Gecko) '
                          'Chrome/73.0.3683.86 Safari/537.36'}

req = urllib.request.Request(url=url,headers=headers1)

rep = urllib.request.urlopen(req)
print(rep.read().decode())

六、百度贴吧例子

import urllib.request
import urllib.parse
import os

'''获取百度贴吧指定吧名和页码的帖子,并写入指定文件'''

url = 'http://tieba.baidu.com/f?ie=utf-8&'

headers1 = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                             'AppleWebKit/537.36 (KHTML, like Gecko) '
                              'Chrome/73.0.3683.86 Safari/537.36'}

ba_name = input("请输入贴吧名：")
start_page = int(input("请输入起始页码："))
end_page = int(input("请输入结束页码："))

if not os.path.exists(ba_name):
    os.mkdir(ba_name)

for page in range(start_page,end_page+1):

    data = {'kw':ba_name,
            'pn':'(page-1)*50',}      #参数设置

    form_data = urllib.parse.urlencode(data)    #将字典格式的数据转为url格式
    post_url = url + form_data     #拼接url

    req = urllib.request.Request(url=post_url,headers=headers1)     #创建请求对象

    rep = urllib.request.urlopen(req)        #发送请求

    ret = rep.read()

    filename = str(page) + '.html'
    filepath = ba_name + '/' + filename
    with open(filepath,'wb') as fp:
        fp.write(ret)

七、urlError

import urllib.request
import urllib.parse
import urllib.error

url = 'http://www.maodan.com'

'''Exception:万能的异常捕获类'''
# try:
#     rep = urllib.request.urlopen(url)
#     print(rep)
# except Exception as e:
#     print(e)

'''用URLError精确捕获'''
try:
    rep = urllib.request.urlopen(url)
    print(rep)
except urllib.error.URLError as e:
    print(e)

八、HTTPError

import urllib.request
import urllib.parse
import urllib.error

url = 'https://www.cnblogs.com/java-chen-hao/p/1108374.html'

'''用URLError精确捕获'''
try:
    rep = urllib.request.urlopen(url)
    print(rep)
except urllib.error.HTTPError as e:
    print(e)
except urllib.error.URLError as e:
    print(e)
'''HTTPError是URLError的子类，都能捕获httpError。
   两者同时捕获时，HTTPError写在前面。儿子先上，儿子不行父亲上'''

九、handler与opener

import urllib.request
import urllib.parse

url = 'http://www.baidu.com/'

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                         'AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'}

'''创建一个HTTPhandler'''
my_handler = urllib.request.HTTPHandler()
'''通过handler创建一个opener'''
my_opener = urllib.request.build_opener(my_handler)

'''构建请求对象'''
req = urllib.request.Request(url,headers=headers)
'''发送请求'''
rep = my_opener.open(req)
print(rep.read().decode())

十、代码配置代理

import urllib.request
import urllib.parse

'''创建一个Proxyhandler'''
my_handler = urllib.request.ProxyHandler({'http':'114.215.95.188:3128'})

my_opener = urllib.request.build_opener(my_handler)

'''百度查询IP地址的URL'''
url = 'https://www.baidu.com/s?ie=utf-8&wd=IP'

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) '
                         'AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'}

req = urllib.request.Request(url,headers=headers)

rep = my_opener.open(req)

with open('ip.html','wb') as fp:
    fp.write(rep.read())